806 lines
17 KiB
NASM
806 lines
17 KiB
NASM
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page ,132
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subttl emmain.asm - Main Entry Point and Address Calculation Procedure
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;***
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;emmain.asm - Main Entry Point and Address Calculation Procedure
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;
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; Copyright (c) 1987-89, Microsoft Corporation
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;
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;Purpose:
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; Main Entry Point and Address Calculation Procedure
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;
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; This Module contains Proprietary Information of Microsoft
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; Corporation and should be treated as Confidential.
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;
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;Revision History:
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; See emulator.hst
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;
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;*******************************************************************************
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;*********************************************************************;
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; ;
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; Main Entry Point and Address Calculation Procedure ;
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; ;
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;*********************************************************************;
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;
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; This routine fetches the 8087 instruction, calculates memory address
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; if necessary into ES:SI and calls a routine to emulate the instruction.
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; Most of the dispatching is done through tables. (see comments in CONST)
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ProfBegin MAIN
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ifdef XENIX
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ifdef i386
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LDT_DATA= 02Fh ; UNDONE - 386 emulator data LDT
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else
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LDT_DATA= 037h ; UNDONE - 286 emulator data LDT
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endif ;i386
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endif ;XENIX
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ifdef PROTECT
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; protect mode Segment override case
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glb <protSegOvrTab>
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protSegOvrTab label word
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dw DSSegOvr ; 11
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dw ESSegOvr ; 00
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dw CSSegOvr ; 01
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dw SSSegOvr ; 10
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endif ;PROTECT
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ifdef DOS3
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; isolated FWAIT
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ifdef WINDOWS
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pub FWtrap
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cld ; this CLD is a nop.
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iret
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else ;not WINDOWS
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pub FWtrap
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PUSH BP ; fix up isolated FWAIT
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PUSH DS
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PUSH SI
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MOV BP,SP ; Point to stack
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LDS SI,DWORD PTR 6[BP] ; Fetch ret address,(points to after instruction)
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DEC SI ; Make DI point to instruction
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DEC SI
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MOV 6[BP],SI ; Change ret address to return to instruction
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mov word ptr [si],0C0h*256+89h ; change interrupt to mov ax,ax
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POP SI
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POP DS
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POP BP
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IRET ; interrupt return
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endif ;not WINDOWS
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; Segment override case
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glb <SegOvrTab>
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SegOvrTab label word
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dw DSSegOvr
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dw SSSegOvr
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dw CSSegOvr
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dw ESSegOvr
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pub SOtrap
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STI ; re-enable interrupts
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push ax
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push es ; set up frame
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push ds
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push di
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push si
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push dx
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push cx
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push bx
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sub sp,2 ; reserve for regSegOvr
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push bp
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mov bp,sp ; set up frame pointer
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CLD ; clear direction flag forever
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; get address mode information, dispatch to address calculation
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MOV DX,BX ; may use original BX to calc address
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MOV AX,DI ; may use original DI to calc address
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LDS DI,dword ptr [bp].regIP ; DS:DI is caller's CS:IP
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INC DI ; increment past operation byte
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INC DI ; increment past operation byte
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MOV CX,[DI-2] ; get trap number, opcode (DS=caller CS)
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mov bx,cx ; upper 2 bits indicate segment override
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rol bl,1
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rol bl,1
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and bx,3
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rol bx,1
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jmp SegOvrTab[bx]
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endif ;DOS3
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pub DSSegOvr ; 00
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mov es,[bp].regDS ; set ES to EA segment
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jmp short ESSegOvr
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pub CSSegOvr ; 10
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mov bx,ds ; DS = caller's CS
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mov es,bx ; set ES to EA segment
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jmp short ESSegOvr
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pub SSSegOvr ; 01
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mov bx,ss ; SS = caller's SS
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mov es,bx ; set ES to EA segment
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pub ESSegOvr ; 11
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mov [bp].regSegOvr,es ; save for bp rel EAs
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jmp short CommonDispatch
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ifdef PROTECT
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pub protSegOvr
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mov dx,bx ; may use original BX to calc address
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mov bl,cl
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.286
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shr bl,2
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ifndef DOS5only
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.8086
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endif
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and bx,6 ; bl = (seg+1) and 6
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inc di ; point to displacement
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mov cx,[di-2] ; cx = esc 0-7 and opcode
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jmp protSegOvrTab[bx] ; process appropriate segment override
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ifdef XENIX
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pub jinstall
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jmp installemulator
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endif ;XENIX
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pub protemulation
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cld ; clear direction flag forever
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ifdef XENIX
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push ax ; UNDONE - slow
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push ds ; UNDONE - slow
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mov ax,LDT_DATA ; load up emulator's data segment
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mov ds,ax
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cmp [Einstall],0 ; check if emulator is initialized
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je jinstall ; no - go install it
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pub protemcont
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pop ds ; UNDONE - slow
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pop ax ; UNDONE - slow
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endif ;XENIX
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push ax
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push es ; set up frame
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push ds
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push di
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push si
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push dx
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push cx
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push bx
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push ss ; save SegOvr (bp forces SS override)
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push bp
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mov bp,sp ; set up frame pointer
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mov dx,ds ; save original DS for default case
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mov ax,di ; may use original DI to calc address
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lds di,dword ptr [bp].regIP ; ds:di = 287 instruction address
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mov cx,[di] ; cx = esc 0-7 and opcode
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add di,2 ; point to displacement
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add cl,28h ; set carry if esc 0-7 (and cl = 0-7)
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jnc protSegOvr ; no carry - must be segment override
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mov es,dx ; es = user data segment
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mov dx,bx ; may use original BX to calc address
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endif ;PROTECT
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ifdef DOS3and5
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jmp short CommonDispatch
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endif ;DOS3and5
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ifdef DOS3
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; normal entry point for emulator interrupts
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even
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pub DStrap
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STI ; re-enable interrupts
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push ax
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push es ; set up frame
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push ds
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push di
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push si
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push dx
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push cx
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push bx
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push ss ; save SegOvr (bp forces SS override)
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push bp
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mov bp,sp ; set up frame pointer
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mov ax,ds
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mov es,ax ; ES = caller's DS
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CLD ; clear direction flag forever
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; get address mode information, dispatch to address calculation
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MOV DX,BX ; may use original BX to calc address
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MOV AX,DI ; may use original DI to calc address
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LDS DI,dword ptr [bp].regIP ; DS:DI is caller's CS:IP
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INC DI ; increment past operation byte
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MOV CX,[DI-2] ; get trap number, opcode (DS=caller CS)
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; Otherwise, CL contains BEGINT + |MF|Arith| so we must unbias it
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SUB CL,BEGINT
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endif ;DOS3
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; DS:DI = original CS:IP of displacement field
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; ES = Effective Address segment (original DS if no segment override)
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; DX = original BX
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; AX = original DI
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; SI = original SI
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; CX = (opcode,0-7 from ESC byte)
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; stack = saved register set
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pub CommonDispatch
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ROL CH,1 ; rotate MOD field next to r/m field
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ROL CH,1
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MOV BL,CH ; get copy of operation
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AND BX,1FH ; Mask to MOD and r/m fields
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SHL BX,1 ; make into word offset
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JMP EA286Tab[BX]
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OneByteDisp macro
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mov al, [di] ;; get one byte displacement
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cbw ;; sign extend displacement
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inc di ;; get past displacement byte
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add si, ax ;; add one byte displacement
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endm
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TwoByteDisp macro
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add si, [di] ;; add word displacement
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add di, 2 ;; get past displacement word
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endm
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even
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pub BXXI0D
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MOV SI,DX ; use original BX index value
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JMP short ADRFIN ; have offset in SI
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pub DSDI0D
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MOV SI,AX ; use alternate index value
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JMP short ADRFIN ; have offset in SI
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even
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pub BPXI1D
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mov SI,[bp].regBP ; add original BP value
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mov es,[bp].regSegOvr ; ES = override segment (or SS if none)
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OneByteDisp
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JMP short ADRFIN
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even
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pub BPDI1D
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MOV SI,AX ; use alternate index value
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pub BPSI1D
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ADD SI,[bp].regBP ; add original BP value
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mov es,[bp].regSegOvr ; ES = override segment (or SS if none)
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OneByteDisp
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JMP short ADRFIN
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even
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pub BXSI1D
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MOV AX,SI ; really will want SI, not DI
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pub BXDI1D
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ADD DX,AX ; now DX is original BX plus index
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pub BXXI1D
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MOV AX,DX ; use original BX index value
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pub DSDI1D
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MOV SI,AX ; use alternate index value
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pub DSSI1D
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OneByteDisp
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JMP short ADRFIN
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even
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pub BPXI2D
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mov SI,[bp].regBP ; add original BP value
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mov es,[bp].regSegOvr ; ES = override segment (or SS if none)
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TwoByteDisp
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JMP short ADRFIN
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even
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pub BPDI2D
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MOV SI,AX ; use alternate index value
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pub BPSI2D
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ADD SI,[bp].regBP ; add original BP value
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mov es,[bp].regSegOvr ; ES = override segment (or SS if none)
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TwoByteDisp
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JMP short ADRFIN
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even
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pub BXSI2D
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MOV AX,SI ; really will want SI, not DI
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pub BXDI2D
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ADD DX,AX ; now DX is original BX plus index
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pub BXXI2D
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MOV AX,DX ; use original BX index value
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pub DSDI2D
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MOV SI,AX ; use alternate index value
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pub DSSI2D
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TwoByteDisp
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JMP short ADRFIN
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even
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pub BPDI0D
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MOV SI,AX ; use alternate index value
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pub BPSI0D
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add si,[bp].regBP ; really will want BP, not BX
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mov es,[bp].regSegOvr ; ES = override segment (or SS if none)
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jmp short ADRFIN
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even
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pub BXDI0D
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MOV SI,AX ; si = regDI
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pub BXSI0D
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add si,dx ; si = regSI+regBX
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jmp short ADRFIN
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even
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pub DSXI2D
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MOV SI,[DI] ; get two byte displacement
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INC DI ; get past displacement byte
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INC DI ; get past displacement byte
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pub DSSI0D ; SI = EA (original SI for DSSI0D)
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pub ADRFIN
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MOV [bp].regIP,DI ; final return offset
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ifdef LOOK_AHEAD
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mov bl,[di] ; get byte of next instruction
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endif
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ifdef MTHREAD
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LOADthreadDS ; macro in emthread.asm
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; loads thread's DS, trashes AX
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else ;not MTHREAD
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ifdef standalone
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xor ax,ax
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mov ds,ax
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mov ds,ds:[4*TSKINT+2] ; DS = emulator task data segment
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elseifdef XENIX
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mov ax,LDT_DATA
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mov ds,ax
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elseifdef _COM_
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mov ds, [__EmDataSeg]
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else
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mov ax, edataBASE
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mov ds,ax
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endif
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endif ;not MTHREAD
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ifdef LOOK_AHEAD
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mov [NextOpCode], bl ; save byte of next instruction
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endif
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mov [CURerr],MemoryOperand ; clear current error, set mem. op bit
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; At this point ES:SI = memory address, CX = |Op|r/m|MOD|escape|MF|Arith|
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SHR CH,1
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SHR CH,1 ; Move Op field to BX for Table jump
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SHR CH,1
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SHR CH,1
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MOV BL,CH
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AND BX,0EH
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|
|
TEST CL,1 ; Arith field set?
|
||
|
|
JZ ArithmeticOpMem
|
||
|
|
|
||
|
|
pub NonArithOpMem
|
||
|
|
mov eax,offset EMLFINISH
|
||
|
|
push eax
|
||
|
|
jmp NonArithOpMemTab[BX]
|
||
|
|
|
||
|
|
even
|
||
|
|
|
||
|
|
pub ArithmeticOpMem
|
||
|
|
PUSH BX ; Save Op while we load the argument
|
||
|
|
MOV BX,CX ; Dispatch on MF
|
||
|
|
AND ebx,6H
|
||
|
|
ifdef i386
|
||
|
|
call FLDsdriTab[2*ebx] ; emulate proper load
|
||
|
|
else
|
||
|
|
call FLDsdriTab[ebx] ; emulate proper load
|
||
|
|
endif
|
||
|
|
POP BX
|
||
|
|
|
||
|
|
mov ax,ds ; ES = DS = task data area
|
||
|
|
mov es,ax
|
||
|
|
MOV SI,[CURstk] ; address top of stack
|
||
|
|
MOV DI,SI
|
||
|
|
ChangeDIfromTOStoNOS
|
||
|
|
MOV [RESULT],DI ; Set up destination Pointer
|
||
|
|
|
||
|
|
JMP short DoArithmeticOpPop
|
||
|
|
|
||
|
|
|
||
|
|
even
|
||
|
|
|
||
|
|
pub NoEffectiveAddress ; Either Register op or Miscellaneous
|
||
|
|
|
||
|
|
MOV [bp].regIP,DI ; final return offset
|
||
|
|
|
||
|
|
ifdef LOOK_AHEAD
|
||
|
|
mov bl, [di] ; get first byte of next instruction.
|
||
|
|
endif
|
||
|
|
|
||
|
|
ifdef MTHREAD
|
||
|
|
LOADthreadDS ; macro in emthread.asm
|
||
|
|
; loads thread's DS; trashes AX
|
||
|
|
mov ax,ds
|
||
|
|
mov es,ax ; DS = ES = per-thread em. data area
|
||
|
|
xor ax,ax
|
||
|
|
|
||
|
|
else ;not MTHREAD
|
||
|
|
|
||
|
|
xor ax,ax
|
||
|
|
|
||
|
|
ifdef standalone
|
||
|
|
mov ds,ax
|
||
|
|
mov di,ds:[4*TSKINT+2] ; DI = emulator task data segment
|
||
|
|
|
||
|
|
elseifdef XENIX
|
||
|
|
mov di,LDT_DATA
|
||
|
|
|
||
|
|
elseifdef _COM_
|
||
|
|
mov di, [__EmDataSeg]
|
||
|
|
|
||
|
|
else
|
||
|
|
mov di, edataBASE
|
||
|
|
endif
|
||
|
|
|
||
|
|
mov ds,di ; di = emulator data segment
|
||
|
|
mov es,di ; ax = 0
|
||
|
|
endif ;not MTHREAD
|
||
|
|
|
||
|
|
; ES = emulator data segment
|
||
|
|
; DS = emulator data segment
|
||
|
|
; AX = 0
|
||
|
|
|
||
|
|
ifdef LOOK_AHEAD
|
||
|
|
mov [NextOpCode], bl ; save first byte of next instruction
|
||
|
|
endif
|
||
|
|
|
||
|
|
mov [CURerr],ax ; clear current error, memory op bit
|
||
|
|
|
||
|
|
; CX = |Op|r/m|MOD|escape|MF|Arith|
|
||
|
|
|
||
|
|
MOV BL,CH
|
||
|
|
SHR BL,1 ; Mov Op field to BX for jump
|
||
|
|
SHR BL,1
|
||
|
|
SHR BL,1
|
||
|
|
SHR BL,1
|
||
|
|
AND BX,0EH
|
||
|
|
|
||
|
|
TEST CL,1 ; Arith field set?
|
||
|
|
JZ ArithmeticOpReg
|
||
|
|
|
||
|
|
pub NonArithOpReg
|
||
|
|
CALL NonArithOpRegTab[BX]
|
||
|
|
JMP EMLFINISH
|
||
|
|
|
||
|
|
; For register arithmetic operations, one operand is always the stack top.
|
||
|
|
; The r/m field of the instruction is used to determine the address of
|
||
|
|
; the other operand (ST(0) - ST(7))
|
||
|
|
; CX = xxxRRRxxxxxxxxxx (x is don't care, RRR is relative register # 0-7)
|
||
|
|
|
||
|
|
even
|
||
|
|
|
||
|
|
pub ArithmeticOpReg
|
||
|
|
|
||
|
|
call RegAddr ;di <= address of 2nd operand
|
||
|
|
;carry set if invalid register
|
||
|
|
jc InvalidOperand ;no, invalid operand, don't do operation
|
||
|
|
|
||
|
|
MOV [RESULT],SI ; Set destination to TOS
|
||
|
|
TEST CL,04H ; Unless Dest bit is set
|
||
|
|
JZ DestIsSet ; in which case
|
||
|
|
MOV [RESULT],DI ; Set destination to DI
|
||
|
|
|
||
|
|
pub DestIsSet
|
||
|
|
; Need to Toggle Reverse bit for DIV or SUB
|
||
|
|
TEST BL,08H ; OP = 1xx for DIV and SUB; BX = |0000|OP|O|
|
||
|
|
JZ SetUpPop
|
||
|
|
XOR BL,02H ; Toggle Reverse bit
|
||
|
|
|
||
|
|
pub SetUpPop
|
||
|
|
TEST CL,02H
|
||
|
|
JZ DoArithmeticOpNoPop
|
||
|
|
|
||
|
|
pub DoArithmeticOpPop
|
||
|
|
CALL ArithmeticOpTab[BX]
|
||
|
|
mov esi,[CURstk]
|
||
|
|
cmp esi,[BASstk] ; 15 was it last register in the chunk ?
|
||
|
|
jz short AOPstovr ; 16 yes, overflow
|
||
|
|
AOPstok:
|
||
|
|
sub esi,Reg87Len ; 4 decrement SI to previous register
|
||
|
|
mov [CURstk],esi ; 15 set current top of stack
|
||
|
|
JMP short EMLFINISH
|
||
|
|
|
||
|
|
AOPstovr:
|
||
|
|
call UnderStk ; stack underflow error
|
||
|
|
jmp AOPstok
|
||
|
|
|
||
|
|
even
|
||
|
|
|
||
|
|
pub DoArithmeticOpNoPop
|
||
|
|
mov eax,offset EMLFINISH
|
||
|
|
push eax
|
||
|
|
jmp ArithmeticOpTab[BX]
|
||
|
|
|
||
|
|
|
||
|
|
;*** InvalidOperand - register operand does not exist
|
||
|
|
;
|
||
|
|
; RETURNS
|
||
|
|
; sets Stack Underflow and Invalid bits in [CURerr]
|
||
|
|
;
|
||
|
|
; DESCRIPTION
|
||
|
|
; a reference was made to a register that does not
|
||
|
|
; exist on the stack. Set error bits and exit.
|
||
|
|
|
||
|
|
pub InvalidOperand
|
||
|
|
call UnderStk ;indicate stack underflow error
|
||
|
|
or [CURerr],Invalid ;indicate invalid operand
|
||
|
|
jmp short EMLFINISH ;don't execute instruction
|
||
|
|
|
||
|
|
;*** RegAddr - compute register address
|
||
|
|
;
|
||
|
|
; ARGUMENTS
|
||
|
|
; CX = |Op|r/m|MOD|esc|MF|Arith|
|
||
|
|
; r/m = register whose address is to be computed
|
||
|
|
;
|
||
|
|
; RETURNS
|
||
|
|
; SI = address of top of stack
|
||
|
|
; DI = address of requested register
|
||
|
|
; PSW.C set if register is not valid
|
||
|
|
; PSW.C reset if register is valid
|
||
|
|
;
|
||
|
|
; DESCRIPTION
|
||
|
|
; multiply register number by 12 and subtract this from
|
||
|
|
; [CURstk] (the address of TOS) to compute address of
|
||
|
|
; register referenced by r/m.
|
||
|
|
;
|
||
|
|
; REGISTERS
|
||
|
|
; modifies dx
|
||
|
|
|
||
|
|
pub RegAddr
|
||
|
|
MOV SI,[CURstk] ; address top of stack
|
||
|
|
MOV DI,SI
|
||
|
|
;set up address of 2nd operand based on r/m field of instruction
|
||
|
|
mov dl,ch ; dl <== byte containing reg#
|
||
|
|
and dl,01ch ; mask all but r/m field
|
||
|
|
|
||
|
|
; Since r/m field contains the relative reg # in bits 2-4 of dl,
|
||
|
|
; and bits 0-1 of dl are zero, dl now contains 4*(reg #). To compute
|
||
|
|
; the memory location of this register, calculate 12*(reg #) and
|
||
|
|
; subtract this from di, which contains the address of the TOS. reg #
|
||
|
|
; is multiplied by 12 because that is the number of bytes in each stack
|
||
|
|
; entry.
|
||
|
|
mov dh,dl ; dh = dl = 4*(reg #)
|
||
|
|
shl dh,1 ; dh = 2*dh = 8*(reg #)
|
||
|
|
add dl,dh ; dl = 8*(reg #) + 4*(reg #) = 12*(reg #)
|
||
|
|
xor dh,dh ; zero out high byte of DX
|
||
|
|
sub di,dx ; di is address of second operand
|
||
|
|
cmp di,[BASstk] ; is register in range?
|
||
|
|
clc ; assume valid register
|
||
|
|
jg $+3 ; valid - skip next instruction
|
||
|
|
cmc ; set carry to indicate invalid register
|
||
|
|
ret
|
||
|
|
|
||
|
|
|
||
|
|
pub CallUnused
|
||
|
|
CALL UNUSED ; Treat as unimpleminted
|
||
|
|
jmp EMLFINISH
|
||
|
|
|
||
|
|
|
||
|
|
; out of line returns from emulator
|
||
|
|
|
||
|
|
|
||
|
|
pub SawException
|
||
|
|
pop bp ; restore registers
|
||
|
|
add sp,2 ; toss regSegOvr
|
||
|
|
pop bx
|
||
|
|
pop cx
|
||
|
|
pop dx
|
||
|
|
pop si
|
||
|
|
pop di
|
||
|
|
pop ds
|
||
|
|
pop es
|
||
|
|
|
||
|
|
pub ExceptionsEmulator
|
||
|
|
JMP CommonExceptions
|
||
|
|
|
||
|
|
|
||
|
|
ifdef LOOK_AHEAD
|
||
|
|
|
||
|
|
pub NoPipeLine
|
||
|
|
|
||
|
|
pop bp ; restore registers
|
||
|
|
add sp,2 ; toss regSegOvr
|
||
|
|
pop bx
|
||
|
|
pop cx
|
||
|
|
pop dx
|
||
|
|
pop si
|
||
|
|
pop di
|
||
|
|
pop ds
|
||
|
|
pop es
|
||
|
|
|
||
|
|
pub errret
|
||
|
|
error_return noerror ; common exit sequence
|
||
|
|
|
||
|
|
endif ;LOOK_AHEAD
|
||
|
|
|
||
|
|
; return from routine; restore registers and return
|
||
|
|
|
||
|
|
|
||
|
|
even
|
||
|
|
|
||
|
|
pub EMLFINISH
|
||
|
|
|
||
|
|
; check for errors
|
||
|
|
|
||
|
|
MOV AX,[CURerr] ; fetch errors
|
||
|
|
or [UserStatusWord],ax ; save all exception errors
|
||
|
|
OR [SWerr],AL ; set errors in sticky error flag
|
||
|
|
NOT AL ; make a zero mean an error
|
||
|
|
MOV bh,byte ptr [UserControlWord] ; get user's IEEE control word
|
||
|
|
OR bh,0C2H ; mask reserved, IEM and denormal bits
|
||
|
|
AND bh,03FH ; unmask invalid instruction,
|
||
|
|
; stack overflow.
|
||
|
|
OR AL,bh ; mask for IEEE exceptions
|
||
|
|
NOT AL ; make a one mean an error
|
||
|
|
TEST AX,0FFFFh-MemoryOperand ; test for errors to report
|
||
|
|
|
||
|
|
jnz SawException ; goto error handler
|
||
|
|
|
||
|
|
ifndef LOOK_AHEAD
|
||
|
|
pop bp ; restore registers
|
||
|
|
add sp,2 ; toss regSegOvr
|
||
|
|
pop bx
|
||
|
|
pop cx
|
||
|
|
pop dx
|
||
|
|
pop si
|
||
|
|
pop di
|
||
|
|
pop ds
|
||
|
|
pop es
|
||
|
|
|
||
|
|
pub errret
|
||
|
|
error_return noerror ; common exit sequence
|
||
|
|
|
||
|
|
else ;LOOK_AHEAD
|
||
|
|
|
||
|
|
|
||
|
|
ifdef DOS3and5
|
||
|
|
jmp [LookAheadRoutine]
|
||
|
|
endif
|
||
|
|
|
||
|
|
|
||
|
|
ifdef DOS3
|
||
|
|
|
||
|
|
pub DOSLookAhead
|
||
|
|
cmp [NextOpcode], fINT ; Quick check. If first byte isn't
|
||
|
|
jne NoPipeLine ; an int instruction then exit.
|
||
|
|
|
||
|
|
; can stay in the emulator - set up registers for CommonDispatch
|
||
|
|
|
||
|
|
mov bp, sp ; set up frame pointer
|
||
|
|
lds di, dword ptr [bp].regIP ; DS:DI = address of next instruction
|
||
|
|
add di, 3 ; skip 3 bytes to displacement field
|
||
|
|
mov cx, [di-2] ; CX = (opcode byte,0-7 from ESC)
|
||
|
|
sub cl, BEGINT
|
||
|
|
|
||
|
|
cmp cl, 7 ; Can't handle segment overrides with
|
||
|
|
ja NoPipeLine ; pipe lining.
|
||
|
|
|
||
|
|
mov ax, [bp].regDI ; ax = original di
|
||
|
|
mov dx, [bp].regBX ; dx = original bx
|
||
|
|
mov si, [bp].regSI ; si = original si
|
||
|
|
mov es, [bp].regDS ; es = original ds (no segment override)
|
||
|
|
mov [bp].regSegOvr, ss ; reset override segment
|
||
|
|
|
||
|
|
rol ch, 1 ; rotate MOD field next to r/m field
|
||
|
|
rol ch, 1
|
||
|
|
mov bl, ch ; get copy of operation
|
||
|
|
and bx, 1fh ; Mask to MOD and r/m fields
|
||
|
|
shl bx, 1 ; make into word offset
|
||
|
|
jmp EA286Tab[bx]
|
||
|
|
|
||
|
|
endif ;DOS3
|
||
|
|
|
||
|
|
|
||
|
|
ifdef PROTECT
|
||
|
|
|
||
|
|
pub ProtLookAhead
|
||
|
|
mov cl, [NextOpcode]
|
||
|
|
|
||
|
|
cmp cl, fFWAIT
|
||
|
|
je CheckNextByte
|
||
|
|
|
||
|
|
cmp cl, iNOP
|
||
|
|
je CheckNextByte
|
||
|
|
|
||
|
|
xor cl, 20h ; See if this is a floating point instruction.
|
||
|
|
cmp cl, 0f8h
|
||
|
|
jbNoPipeLine:
|
||
|
|
jb NoPipeLine
|
||
|
|
|
||
|
|
mov bp, sp ; set up frame pointer
|
||
|
|
lds di, dword ptr [bp].regIP ; ds:di = address of next instruction
|
||
|
|
|
||
|
|
jmp short CanDoPipeLine
|
||
|
|
|
||
|
|
pub CheckNextByte
|
||
|
|
mov bp, sp ; set up frame pointer
|
||
|
|
lds di, dword ptr [bp].regIP ; ds:di = address of next instruction
|
||
|
|
inc di ; next instruction was NOP or FWAIT
|
||
|
|
|
||
|
|
mov cl, [di]
|
||
|
|
xor cl, 20h
|
||
|
|
cmp cl, 0f8h
|
||
|
|
jb jbNoPipeLine
|
||
|
|
|
||
|
|
pub CanDoPipeLine
|
||
|
|
mov ch, [di+1] ; we already have first byte of next
|
||
|
|
add di, 2 ; instruction in cl
|
||
|
|
|
||
|
|
add cl, 8h ; clear out what's left of escape
|
||
|
|
|
||
|
|
mov ax, [bp].regDI ; ax = original di
|
||
|
|
mov dx, [bp].regBX ; dx = original bx
|
||
|
|
mov si, [bp].regSI ; si = original si
|
||
|
|
mov es, [bp].regDS ; es = original ds (no segment override)
|
||
|
|
mov [bp].regSegOvr, ss ; reset override segment
|
||
|
|
|
||
|
|
rol ch, 1 ; rotate MOD field next to r/m field
|
||
|
|
rol ch, 1
|
||
|
|
mov bl, ch ; get copy of operation
|
||
|
|
and bx, 1fh ; Mask to MOD and r/m fields
|
||
|
|
shl bx, 1 ; make into word offset
|
||
|
|
jmp EA286Tab[bx]
|
||
|
|
|
||
|
|
endif ;PROTECT
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
endif ;LOOK_AHEAD
|
||
|
|
|
||
|
|
|
||
|
|
ProfEnd MAIN
|